Patent GB-518794-A (GB)
Title: Improvements relating to automatic grinding or abrading machines
IPC: B24B47/06
Filed: 1938-09-05
Abstract: 518,794. Grinding-machines. NORTON CO. Sept. 5, 1938, No. 25903. Convention date, Oct. 4, 1937. [Class 60] In an automatic grinding-machine for repetition work, for example, grinding the exterior cylindrical surface of hollow work-pieces, a work-piece is held, during grinding, between centres on synchronously rotating spindles and is ground by means of a grinding-wheel mounted on a transverse slide moved rapidly by fluid pressure means up to the work, the feed movement then being slowed down by a dash-pot and continuing until a stop engages a fixed part, when the feed ceases and sparking-out grinding proceeds for a predetermined interval. A work-carrier head is then advanced by fluid pressure means to engage the finished work-piece and also an unground piece in a shoot, the centres simultaneously being withdrawn from the work by fluid pressure means. The head is then tilted to bring the finishing work - piece to a position for discharge to a shoot, and to bring the unground piece opposite the centres, which are then advanced to grip the piece, the cycle being then again repeated. The operations are under the control of a main valve which controls a cycle timing valve, which in turn controls the movements of the work spindles and of a cycle timing cylinder. The machine, described as for plunge - cut grinding, comprises a bed 20 on' which is a longitudinally movable table 21 supporting the work, and a transversely movable, slide 32 carrying a grinding- wheel 34 driven by an electric motor 35. The slide 32 may be moved by hand or automatically by a piston 54 in a cylinder 35, rapid feeding up to the work proceeding until a sleeve 91 adjustably mounted on the piston rod 55 engages dashpot pistons 86, 87, when a slow infeed is given to the wheel 34 until an adjustable sleeve 104 engages a fixed surface 105, the wheel feed then ceasing and sparking-out grinding proceeding for a predetermined interval, after which the wheel is withdrawn rapidly from the work 188 by the piston 54. These movements are controlled by a valve 58 moved in one direction by a spring 82 and in the opposite direction by a solenoid 75 the circuit of which, at the end of the predetermined dwell for sparking-out, is broken by a trip switch 360 operated through a lever 364 by the piston 367 of the cycle timing device. Fluid is supplied to the valve by a pump 59 from a reservoir 61 and the fluid for the dash-pot is maintained by a reservoir 99 fed through a valve 111 and provided with an overflow pipe 112. The work is carried, during grinding, by two heads 115, 116 mounted on a swivel table 119 on the table 21, the heads supporting aligned spindles 117, 118 respectively, which are rotated in synchronism by an electric motor 134 through spur and chain gearing 140 ... 152 ; for ensuring that the two spindles, when these have specially shaped centres may be accurately timed, the sprocket 150 is angularly adjustable relative to the shaft 142. The spindles 117, 118 each comprises a sleeve running in ball oearings 130, 131 pressed by springs 171 to prevent backlash and having slidably keyed therein a sleeve 175 within which is a sleeve 178 pressed in work engaging direction by a spring 179. The sleeve 178 is moved in the opposite direction by a piston 186 in a cylinder 185, the piston being pressed in one direction by springs 187 and having its movement in the opposite direction, under fluid pressure, limited by an adjustable screw stop, which engages a member 191 having a flange movable, with lost motion, in the piston. The sleeve 175 carries a centre 177, which is locked in position by an axial screw 223, and in order that the work may be stripped from the centres, members 215, 219, the latter being adjustable, are provided on the spindles. Work-pieces are supplied from a hopper or magazine 227, down which the pieces roll so as to rest on a surface 285 on which a piece is held by spring fingers 290, and the pieces are removed, for insertion between the centres simultaneously with the removal of a finished work-piece by a workcarrier frame 235 pivoted on a shaft 232 and rockable thereabout by a piston 317 in a cylinder 316 carried by the frame, the piston rod 318 being pivoted to the head supporting bracket 230. The frame has therein a cylinder 245 in which is movable a piston 246, the rod 247 of which carries a cover 249 on which is mounted a head 251 having therein two pockets 252, 253 which, on forward movement of the piston, respectively engage the work-pieces 188a on the surface 285 and a finished work-piece, the pieces being held by spring fingers 256, 260. The frame is then tilted by the movement of the cylinder 316 so that the finished work-piece is moved down to a shoot 300; and the unground piece 188a is moved into alignment with the work centres, which have been withdrawn from the work. The centres then advance to engage the work-pieces, and the frame is withdrawn, the finished piece being released by a lug 301 to roll down the shoot 300. Grinding of the new work-piece then proceeds as above described. The timing of the machine is under the control of a valve 378 having its inlet from the valve 58 through an adjustable throttle valve 396, and fluid from the valve exhausts through an adjustable throttle valve 398, the valves 396, 398 serving to control the rate of movement of the valve piston, and fluid from the valve passes to the cylinder 375 to move the piston 367; the valve also controls the movements of the work spindles and also of the work carrying member 251; the valve also controls the dwell of the grinding- wheel as described above. In order to prevent energization of the solenoid 75 unless the work centres are in operative position, a switch 336 actuated by the piston 186 is provided in the circuit of the solenoid, and a similar switch 345 is provided in connection with the work head 116. Specification 6784/01, [Class 60], is referred to.